1. Field of the Invention
The invention relates generally to luminaires intended for illumination of billboards, outdoor signs and similar vertical surfaces and particularly to luminaires of increased efficiency capable of superior lighting intensities and uniform illumination with reduced light xe2x80x9cspillagexe2x80x9d.
2. Description of the Prior Art
Luminaires capable of illuminating vertical surfaces such as billboards and similar signs occupy a particular niche in the lighting field. Luminaires of this kind must operate in a harsh environment and be effectively impervious to the elements including rain, wind and heat. Prior luminaires developed for illumination of outdoor signs and the like have addressed the requirement that an illumination level of an intensity sufficient to allow the sign being illuminated to be viewed with comprehension from varying distances must be provided. Prior luminaires have also addressed a second requirement that such signs be illuminated to desired levels on various portions thereof to provide a desirable impression of uniformity. Prior luminaires have addressed these two requirements as fully as technology existing at the time permitted. However, as energy conservation considerations have increased in recent times, a further requirement of such luminaires has been to direct as much light as possible of the generated light onto an outdoor sign so that a maximum amount of the generated light is actually used, full utilization of the generated light typically permitting lessened light generation for a given situation with a resultant conservation of energy. In the present marketplace, energy conservation must not result in a reduction in lighting intensity and uniformity. Relatively more recent requirements relating to light xe2x80x9cpollutionxe2x80x9d caused in part by light generated by luminaires that illuminate outdoor signs and the like have resulted in the necessity for the light generated by such luminaires be directed to the greatest degree possible onto the sign or billboard that is to be illuminated rather than xe2x80x9cspillxe2x80x9d about edges of such an outdoor sign, thereby producing stray light that accomplishes no function and acts to obscure the night sky. Light from such luminaires that is not focused onto the billboard or similar sign produces glare and clutter and effectively wastes energy through such inefficiency that the cost of such waste is estimated to exceed as much as one billion dollars on an annual basis. Spill light of this nature can negatively impact tasks performed near the location of an outdoor sign while contributing to xe2x80x9csky glowxe2x80x9d and degrading the nocturnal environment so as to affect the quality of life in rural communities in particular as well as having a negative impact on business and recreational activities.
Luminaires employed for the illumination of outdoor signs and the like have existed for at least the better part of a century as is evidenced by existing United States patents disclosing luminaires for this very purpose. Ennever, in U.S. Pat. No. 2,746,187, describes a system for illumination of an outdoor display such as a billboard or similar outdoor sign, this patent describing luminaires mounted along an upper edge of a billboard and which cast light directly down onto the billboard through direct illumination as well as through reflection from a reflective structure surmounting a light source. Luminaires of the time of Ennever did not produce uniform light intensities over the full surface of a sign and were not energy efficient. In U.S. Pat. No. 3,647,148, Wince discloses luminaire structures having both reflective surfaces and refractive structures configured to direct light onto a particular objective as well as for general illumination. The luminaires disclosed by Wince were not particularly intended for illumination of vertical surfaces. However, the Wince patent provides a disclosure of the use of reflective surfaces and refractive structures for illumination. Odle et al, in U.S. Pat. No. 4,037,341, disclose luminaires intended for illumination of outdoor signs and the like having vertical surfaces intended to be illuminated. By the time of Odle et al, outdoor sign illumination had progressed to the point where a plurality of luminaires mounted in spaced relation to each other and spaced from the sign face to be illuminated were disposed in front of the sign and in proximity to a lower edge of the sign, light generated by the luminaires being directed at angles generally upwardly from said luminaires as opposed to the downward illumination provided by Ennever et al as mentioned above. The patent to Odle et al illustrates an intent to evenly illuminate an outdoor sign with an appropriate intensity and to produce positive side edge cut-off, that is, to minimize light passing from the luminaire and past edges of the sign, the energy generated to produce light not incident on the sign being wasted. Odle et al disclose a combination of reflective surfaces and refractor structures intended to maximize illumination of an outdoor sign given a predetermined amount of generated light. Reibling, in U.S. Pat. No. 4,188,657, describes luminaires intended for the illumination of outdoor signs and being capable of producing light patterns by means of combinations of reflective surface finishes on reflective surfaces of the disclosed luminaires. In U.S. Pat. No. 4,261,030, Hernandez discloses lighting fixtures having horizontally disposed lamps with parabolic reflectors mounted one each behind each of the lamps such that light is directed onto a surface that is to be illuminated. Hernandez discloses auxiliary reflectors in addition to a primary reflector, the combination of reflective surfaces directing light onto a surface that is to be illuminated. U.S. Pat. No. 4,398,239 to de Vos et al discloses a luminaire intended for illuminating roadways and the like including a reflector capable of being removed from a weather-tight housing that also mounts a light source in an operative relation with the reflector. Odle et al, in U.S. Pat. No. 4,451,875, disclose a luminaire intended for illumination of a billboard or the like, the luminaire including reflective surfaces and a light source disposed between the reflective surfaces and a surface of the sign that is to be illuminated. The Odle et al luminaire utilizes refractive structures disposed on and formed integrally with a transparent cover that also comprises a portion of a weather-tight housing. The refractive structures of Odle et al function in concert with reflective surfaces to direct light onto a vertical surface that is to be illuminated such as the face of a billboard or similar outdoor sign. In U.S. Pat. No. 4,559,587, Quiogue et al disclose a luminaire having both reflective surfaces and refractor structures that function cooperatively to direct light onto an objective. Hammond, in U.S. Pat. No. 4,575,783, discloses a reflector configured to direct light emanating from a light source to all areas of an outdoor sign to create a uniform distribution of light on the face of the sign. Light is redirected by the Hammond reflector to portions of the sign surfaces that are not evenly illuminated with an appropriate intensity by light directly incident on the face of the sign from the light source. In U.S. Pat. No. 4,954,935, Hammond et al disclose a lighting system for illuminating an outdoor billboard or the like formed of a number of panels. The system disclosed by Hammond et al utilizes a number of luminaires, one for each panel of the sign. Hammond et al disclose use of a metal halide lamp with reflectors fixed within a lamp housing. The reflectors are positioned behind the lamp and reflect light radiating from the lamp onto the sign surface that is to be illuminated. The reflector of Hammond et al is provided with a number of flutes or reflecting segments. U.S. Pat. No. 4,337,507 to Lasker describes lighting fixtures with directional distributions. Luminaires disclosed by Lasker are provided with a prismatic unit and a reflector unit intended to reduce the amount of light escaping at excessively high angles as is often found with floodlighting luminaires. The prismatic unit disclosed by Lasker employs vertical ribs for directing light produced by a light source and further provides a lateral distribution of light at extremely wide angles as well as illumination behind the aperture of a housing that encloses the prismatic unit and the reflector unit. The light distribution provided by the Lasker structure does not provide a light distribution that can be focused evenly and wholly onto a surface of a vertically oriented billboard or the like. Lasker employs a reflector having a cylindrically and parabolically shaped contour for production of a uniform horizontal distribution of light. Lasker pivots a light source and reflector unit within the housing about a fixed horizontal axis to adjust vertical cut-off angles and angles of maximum intensity. However, the structure of Lasker is not configured for full and even illumination of a vertical surface of a sign or the like as is required for illumination of outdoor advertising signs and the like. Thoman et al, in U.S. Pat. No. 3,358,133, disclose a floodlight having a primary reflector formed in a scoop-like configuration, the reflector being hinged to a supporting frame. A semi-cylindrical auxiliary reflector cooperates with the primary reflector to produce a wide beam uniformly distributed over a large area as is intended by the use of the Thoman et al luminaire as a floodlight. Thoman et al do not disclose optics intended for effective illumination of a vertical surface of an outdoor sign or the like. Subisak et al, in U.S. Pat. Nos. 5,188,453; 5,588,742 and 5,664,878, describe luminaires intended for mounting on a periphery of a sign to illuminate a sign face from internally of such a sign.
As is evidenced by the disclosures of the prior art including those United States patents referred to above, it is seen that substantial efforts have previously been expended toward the goal of uniform illumination of vertical surfaces of billboards, outdoor signs and the like, such illumination being intended to be uniform as well as of a sufficient intensity to permit legible viewing of indicia formed on a sign face and with a desirable utilization of generated light. Although optical systems intended for outdoor sign illumination have taken a number of forms and have been positioned both below and above sign faces, it can be appreciated that improvements in the luminaires themselves are needed in order to maximize light utilization and to reduce light spillage in order to conserve resources including costs required for sign installations. A further intent in the art has been to provide luminaires having efficiencies permitting the utilization of fewer luminaires for illumination of a surface of given dimensions. The present invention addresses these long-felt needs in the art by providing reflective assemblies of particular configuration and that are capable of movement within housings each mounting a light source and reflector structure. The reflective structures of the invention can be formed with reflective surfaces comprised of materials of differing reflectivity in order to tailor light for particular use situations. The reflective structures of the invention further cooperate with refractor structures carried by luminaire housings for redirecting light onto sign surfaces with a minimum of light spillage. The luminaires of the invention exhibit efficiencies permitting utilization of fewer luminaire structures for illumination of sign surfaces of given dimensions. The present invention thus provides substantial advances in the art as will be further appreciated in view of the following disclosure of the several embodiments of the invention.
In the several embodiments of the invention explicitly disclosed herein, the invention provides luminaires intended for illumination of billboards, outdoor signs and similar vertical surfaces and which are capable of uniformly illuminating surfaces of said signs with desired intensity over full surfaces of said signs and with reduced light spillage about edges of such signs. The luminaires of the invention provide improvement over the prior art by the provision of highly efficient primary reflector structures preferably mounted for movement within housings in operative juxtaposition to a light source within each of the housings, each housing being sealed against environmental affects by means of a transparent lens that also functions as a cover. The lens is formed with refractor elements preferably disposed on surfaces of the lens disposed interiorly of the housing. Refractive elements are provided only on portions of the lens and take the form of prisms of differing configuration selected for redirecting light from portions of reflective surfaces of said luminaire to illuminate particular portions of an outdoor sign. Particular shapes of primary reflector structures act to reduce spill light, said reflector structures in certain embodiments being formed of differing metals having different optical characteristics to further enhance sign illumination uniformity while maintaining high average sign illuminance. Primary reflector structures of the invention are preferably provided with side reflectors on each lateral side of each of the primary reflectors, the side reflectors being positioned to increase sign illumination and to decrease spill light. Reflector assemblies formed of the primary reflector structures and associated side reflectors are preferably mounted for pivoting or sliding movement internally of luminaire housings for adjustment of a light pattern directed onto a particular sign. Reflector assembly adjustment can be effected at a manufacturing location or on site. Refractive prisms formed on the transparent luminaire lens refocus direct light from both the light source and the reflector assembly to increase uniformity of illumination and to reduce spill light. Spill light into the night sky is reduced by more than half relative to prior art sign luminaires through use of the present luminaires with improved uniformity of illumination.
Primary reflector structures configured according to the invention essentially take the form of compound parabolic elements formed of smoothly curved sections or reflective segments. Portions of said primary reflectors can be formed of or surfaced with reflective metals having differing optical characteristics such as diffuse, semi-diffuse and specular reflective characteristics. Use of reflector surfaces formed of differing metals having such characteristics allow light to be reflected to form virtual images of the light source distributed over surfaces of the sign with a resultant increase in sign illumination intensity and uniformity of illumination.
Refractive prisms formed along an uppermost portion of the cover act to reduce up-spill light by redirecting light onto top edges of a sign. Prisms located at the bottom portion of the refractor reduce down-spill light by lifting light that would otherwise spill toward bottom corners of a sign.
Efficiencies occasioned by use of the present luminaires permit the use of fewer luminaires for adequate illumination of signs of predetermined dimensions. In the prior art, luminaires intended for illumination of billboards, outdoor signs and the like are capable of desirable illumination of signs of standard dimensions through the use of at least four luminaires. The luminaires of the present invention are capable of desirable illumination of billboards and outdoor signs of the same dimensions through the use of only three of the present luminaires. In other words, in a typical outdoor sign illumination environment, at least four luminaires have been required in the prior art while systems configured with the present luminaires allow the use of only three luminaires for illumination of signs of dimensions previously requiring the use of four prior art luminaires.
Accordingly, it is an object of the invention to provide luminaires intended for illumination of billboards, outdoor signs and the like and which are capable of providing uniform light distribution over full surfaces of said billboards without spillage of light about edges of said billboard.
It is another object of the invention to provide reflector assemblies mounted for adjusting movement within luminaire housings so that the luminaire can be modified either during manufacture or on site for efficient illumination of signs of differing shape and dimension.
It is yet another object of the invention to provide luminaires capable of uniform illumination of billboards and the like with minimum light spillage whereby primary reflectors of curvilinear shape function with refractive prisms carried by the luminaires to direct and/or redirect light onto vertical surfaces of the billboard, said primary reflectors being either smoothly curved or segmented and preferably having side reflectors associated therewith to form reflector assemblies, said side reflectors being either planar, curved or parabolic, or faceted for extremely efficient direction of light onto such a billboard or through refractive prisms carried by luminaire housings for redirecting light onto said billboard.
It is a further object of the invention to provide a luminaire intended for mounting in front of a large panel such as a billboard for illumination of said panel, the luminaire being formed of a housing, a light source disposed within the housing, a primary reflector movably affixed within the interior of the housing for directing light from the light source both directly to surfaces of the panel to be illuminated and to refractive prisms preferably disposed on interior surfaces of a covering lens completing the housing and transparent to light emanating from the light source, from the primary reflector and from side reflectors associated with the primary reflector, the reflective surfaces and the refractive prisms acting to focus light from the light source onto surfaces of the panel with desirable intensity and uniformity and with reduced light spillage.
Yet another object of the invention is to provide a sign lighting luminaire having refractive areas of both prismatic and non-prismatic characteristics disposed on a transparent cover and preferably internally of said cover, these refractive elements being formed in sections disposed at varying locations of the cover and orientations for acting with reflective surfaces of the luminaire to direct light onto a billboard or the like with desirable illumination intensity and uniformity while reducing light spillage.
Still another object of the invention is to provide an outdoor sign illumination system capable of evenly and efficiently illuminating a billboard or the like, said billboard having a typical length-wise dimension of approximately 48 feet in a horizontal sense, such a billboard being fully illuminated by as few as three luminaires configured according to the invention, the luminaires of the invention being capable of illuminating billboards of differing dimensions with fewer luminaires than are required through use of luminaires configured according to the prior art.
Further objects and advantages of the invention will become more readily apparent in light of the following detailed description of the preferred embodiments of the invention.